Estimates Of Life History Parameters Research Articles

Estimation of life history parameters of the Gangetic leaffish, Nandus nandus from southern coastal waters of Bangladesh: implications for sustainable management

Estimation of life history parameters of the Gangetic leaffish, Nandus nandus from southern coastal waters of Bangladesh: implications for sustainable management

The estimation of reproductive values from pedigrees.

Quantifying fitness is important to understand adaptive evolution. Reproductive values are useful for making fitness comparisons involving different categories of individuals, like males and females. By definition, the reproductive value of a category is the expected per capita contribution of the members of that category to the gene pool of future generations. Life history theory reveals how reproductive values can be determined via the estimation of life-history parameters, but this requires an adequate life-history model and intricate algebraic calculations. Recently, an alternative pedigree-based method has become popular, which estimates the expected genetic contribution of individuals to future generations by tracking their descendants down the pedigree. This method is versatile and intuitively appealing, but it is unknown if the method produces estimates of reproductive values that are accurate and precise. To investigate this, we implement various life-history scenarios (for which the "true" reproductive values can be calculated) in individual-based simulations, use the simulation data to estimate reproductive values with the pedigree method, and compare the results with the true target values. We show that the pedigree-based estimation of reproductive values is either biased (in the short term) or imprecise (in the long term). This holds even for simple life histories and under idealized conditions. We conclude that the pedigree method is not a good substitute for the traditional method to quantify reproductive values.

Long‐term ecological data confirm and refine conservation assessment of critically endangered swift parrots

AbstractConservation assessments of threatened species are often limited by scarce data and parameter uncertainty. Predictive models, designed to incorporate this uncertainty, may be the only tool available to inform conservation assessments for data‐deficient species, but they are used surprisingly rarely for this purpose. The swift parrotLathamus discoloris the only critically endangered bird to be listed in Australia based on population viability analysis (PVA). We aimed to evaluate the accuracy of the 2015 conservation assessment, which used sparse information, by incorporating new detailed and long‐term data. First, we updated a range of life history parameter estimates, and then we repeated the same PVA as per the original conservation assessment. This process confirmed our earlier finding that swift parrot nests were more likely to survive in places with high mature forest cover. We identify that high forest landscape integrity and abundant hollow‐bearing trees best predict nest daily survival rates. Based on the updated PVA, we predict a 92.3% population decline over three generations (11 years). This supported the predictions of the original conservation assessment, and the main benefit of the additional data was improved confidence in projections (the magnitude and direction of the population decline were similar between the original and updated PVAs). Our results demonstrate that meaningful trends can be inferred for species with imperfect information about their life history. Using predictive models like PVAs can help managers identify which life history parameters impact most on demographic trends. This information can guide targeted data collection so that ‘draft’ models can be later updated to improve certainty around population predictions.

Body growth and reproductive parameters of common dolphins from the southwestern Atlantic

AbstractCommon dolphins, Delphinus delphis, in the southwestern Atlantic Ocean are subject to incidental mortality in fishing gear. However, no information on trends in abundance or estimates of bycatch mortality are available to evaluate the impact of this threat on the population. This study presents estimates of life history parameters using postmortem data obtained over a 17‐year period in Argentina. Ages were determined for 93 specimens, and reproductive organ samples were examined (n = 89). Immature animals ranged from 0 to 6 years in females and from 0 to 9 years in males. Mature animals ranged from 7 to 21 years in females and from 6 to 23 years in males. The asymptotic body length (L∞) described by a Gompertz model fit to age‐length data was 196 cm, 95% CI [192.45, 199.76] for females and 210.75 cm, 95% CI [206.64, 215.30] for males and was attained at 14 years in females and 15 years in males. Comparison to other populations showed that L∞ were shorter than estimates from New Zealand, similar to L∞ from eastern North Atlantic, and longer than estimates from North Pacific common dolphins. Lmax reported here were shorter than New Zealand ones but similar to those previously reported from other populations.

Age, growth, and mortality of littlehead porgy, Calamus proridens, from southeast Florida coastal waters

Sectioned otoliths were used to age littlehead porgy Calamus proridens ( n = 737) from southeastern Florida recreational fisheries. Otolith sections contained easily identifiable annuli and were reliable structures for aging littlehead porgy up to 11 yrs. Opaque zones were deposited from March to June (peaking in April). Littlehead porgy ranged from 1 to 11 yrs and 220 to 385 mm total length (TL). Body size relationships were TL = 1.09 FL + 16.06 ( n = 3474, r2 = 0.95), FL = 0.87 TL – 1.15 ( n = 3474, r2 = 0.95), W = 4.76 × 10 –5 TL 2.80 ( n = 6722, r2 = 0.86), and W = 1.2 × 10 –4 FL 2.71 ( n = 3474, r2 = 0.90), where W is total weight (g) and FL is fork length (mm). Growth was not significantly different between two discrete geographic regions of Florida, and the von Bertalanffy growth equation was Lt = 335 (1 – e –0.41 ( t + 2.13) ) for all areas combined. The point estimate of natural mortality was M = 0.38, while age-specific estimates of M ranged from 0.60 to 0.41 yrs–1 for ages 1–11. Littlehead porgy were fully recruited to the headboat fishery by age- 3 and catch curve analysis resulted in an estimate of total mortality Z = 1.08 for ages 3–7+. This study reports first estimates of life history parameters for littlehead porgy from Atlantic waters of the southeastern United States.

Modelling the effects of variation in growth, recruitment, and harvest on lake sturgeon population viability and recovery

Abstract Regulatory agencies and fisheries managers tasked with implementing recovery plans for endangered species must frequently make decisions based on limited data, while also considering general uncertainty associated with prediction. Population viability analysis (PVA) is a modelling tool that is particularly useful for long‐lived species and can be applied even in the absence of robust estimates of life history parameters. As empirical data are accumulated over time, PVA inputs, model structure, and parameter estimates can be refined to increase model realism and accuracy. Since the first iterations of lake sturgeon (Acipenser fulvescens) PVA were run, approximately 15 years ago, based on conservative inputs for Canadian population units, important empirical data have accumulated from a variety of river systems that the species inhabits. Erratic recruitment patterns have been revealed, juvenile survival has been determined to be higher than initially believed, and growth rates have been found to vary by habitat (river) type. Exploiting an improved biological understanding of the species, somatic growth models derived from three well‐studied lake sturgeon populations were used to examine the effects of recruitment variability and incremental levels of adult harvest (mortality) on the probability of population recovery and risk of population decline. A total of 110 PVA scenarios (with 1,000 replicates per scenario) were run for each of the three somatic growth models (slow, medium, and fast). The PVA results suggest that the recovery potential for lake sturgeon populations may be higher than previous models, based on conservative inputs, have indicated. A few scenarios resulted in recovery after 100 years, and nearly half of the scenarios resulted in recovery after 250 years. Similarly, the probability of decline for small populations was most sensitive to adult harvest, with little change in the number of scenarios resulting in decline at the time points of 100, 250, and 500 years. A worked example highlights how the targeted monitoring of both juvenile and adult life stages can be used to evaluate the recovery potential of more than one population and prioritize management initiatives, such as harvest reduction and stocking.

Stock Assessment of Small Yellow Croaker (Larimichthys polyactis) Off the Coast of China Using Per-Recruit Analysis Based on Bayesian Inference

This paper presents a framework for quantifying uncertainty in per-recruit analysis for small yellow croaker (Larimichthys polyactis) fisheries in China, in which credible estimates of life history parameters from Bayesian inference were used to generate the distribution for a quantity of interest. Small yellow croakers were divided into five spatial groups. The status of each group was examined using a yield-per-recruit (YPR) model and a spawning stock biomass-per-recruit (SSBPR) model. The optimal length at first capture (Lcopt) was proposed to recover the biomass. The maximum observed age in the current stocks (3 years) and the maximum recorded age (≥20 years) were adopted in per-recruit analysis. Our results suggest that the framework can quantify uncertainty well in the output of per-recruit analysis for small yellow croaker. It is suited to other fish species. The SSBPR at FMSY (SSBPRMSY) is a better benchmark than the spawning potential ratio (SPR) at FMSY because SSBPRMSY had a unimodal distribution. The SSBPR analysis can lead to a more conservative Lcopt than the YPR analysis. The key factor influencing the assessment conclusions may be the growth parameters rather than the natural mortality rate for a stock with a younger maximum age. Overfishing likely occurred for all groups and recruitment overfishing may not occur if the maximum age is maintained at 3 years. Increasing lengths at first capture to the recommended values can help this population recover. However, Fcur is too high for small yellow croakers to attain the maximum recorded age. Both reducing fishing mortality rate and increasing length at first capture are needed to attain the maximum recorded age.

Fine-scale estimation of key life-history parameters of malaria vectors: implications for next-generation vector control technologies

BackgroundMosquito control has the potential to significantly reduce malaria burden on a region, but to influence public health policy must also show cost-effectiveness. Gaps in our knowledge of mosquito population dynamics mean that mathematical modelling of vector control interventions have typically made simplifying assumptions about key aspects of mosquito ecology. Often, these assumptions can distort the predicted efficacy of vector control, particularly next-generation tools such as gene drive, which are highly sensitive to local mosquito dynamics.MethodsWe developed a discrete-time stochastic mathematical model of mosquito population dynamics to explore the fine-scale behaviour of egg-laying and larval density dependence on parameter estimation. The model was fitted to longitudinal mosquito population count data using particle Markov chain Monte Carlo methods.ResultsBy modelling fine-scale behaviour of egg-laying under varying density dependence scenarios we refine our life history parameter estimates, and in particular we see how model assumptions affect population growth rate (Rm), a crucial determinate of vector control efficacy.ConclusionsSubsequent application of these new parameter estimates to gene drive models show how the understanding and implementation of fine-scale processes, when deriving parameter estimates, may have a profound influence on successful vector control. The consequences of this may be of crucial interest when devising future public health policy.Graphical abstract

From Amazon Catfish to Mekong Money Fish: Size‐based Assessment of Data‐Limited Commercial Inland Fisheries

Inland fisheries are often complex, spatially dispersed, and seasonal. A lack of monitoring can result in unreliable or incomplete catch data, suggesting a role for assessment methods based on population size structure. This paper evaluates and compares empirical size‐based indicators and the length‐based spawning potential ratio model as candidate tools for assessing data‐limited commercial fisheries in inland systems. Case study applications are presented for a contrasting set of important fisheries in the Amazon Basin (Brazil, Bolivia, Colombia, and Peru), the Tonlé Sap River (Cambodia), Paraná River (Argentina), and Bayano Reservoir (Panama). These case studies were selected to explore the effects on assessment of factors including lack of life history information, spatial separation of life history stages, modality in population size structure of floodplain river fish, and fishing gear selectivity. An international workshop was organized to bring together experts from the study systems and elsewhere to discuss the results, and to highlight potential issues and caveats. It was concluded that length‐based models may work well in cases where size‐selective gears are used to target a few larger species with reliable life history parameter estimates. Empirical surveillance indicators are more flexible for integrating quantitative data with local expert knowledge in common data‐poor situations. In general, size‐based assessment can provide guidance for the sustainable management of target species in diverse inland fisheries.

Review of life history parameters and preliminary age estimates of some New Zealand deep-sea fishes

ABSTRACT A literature review on longevity of New Zealand deep-sea fishes provided life history parameter estimates for 17 bony and five cartilaginous species. Preliminary age estimates for a further nine deep-sea bony fishes were made from otolith zone counts and included results from a pilot analysis of radiocarbon age estimates from the otoliths of three of the species. Radiocarbon age estimates corroborated the otolith zone count age estimates made for white rattail (Trachyrincus aphyodes) and smallhead cod (Lepidion microcephalus) but were substantially lower for the third species, smallscale brown slickhead (Alepocephalus antipodianus) which suggested that it was not exposed to elevated (near-surface) levels of 14C in early life. Validation of otolith zone age estimates is difficult for deep-sea species but the radiocarbon analysis provided a practical method to corroborate age estimates for some bony fishes. Of the 31 fish in this study (known and new age estimates), five of the fishery target species and 10 of the bycatch were long-lived (50 years or more). The hypothesis that all New Zealand deep-sea species are long-lived was not supported, but the chance of a species being long-lived seem to be higher in deeper water.

Dome-shaped selectivity in LB-SPR: Length-Based assessment of data-limited inland fish stocks sampled with gillnets

Inland fisheries can support complex social-ecological systems and contribute to food security. However, many target stocks lack monitoring and quantitative assessment. There may be scope to apply current data-limited assessment models in these fisheries. The Length-Based Spawning Potential Ratio (LB-SPR) model requires only fish length data and input estimates of key life history parameters. LB-SPR has been seldom applied in inland systems, partly due to the current model assumption of asymptotic fishing gear selection, characteristic of trawls. In contrast, most inland fisheries operate gillnets or hooks, having dome-shaped selection curves. This is problematic because the largest size classes of fish are not fully retained by the gear, but their absence in the catch will be assumed by the LB-SPR model to reflect fishing mortality. LB-SPR was extended to include dome-shaped selection. Case study assessments were undertaken using survey gillnet catches of brown trout Salmo trutta from four Irish lakes. Bayesian Monte Carlo methods were used to quantify uncertainty around estimates of life history parameters for each stock. Despite small sample sizes, the model produced estimates of SPR that corresponded to expert knowledge of stock status. The extended LB-SPR can be applied to assess data-limited inland fish stocks, and other stocks for which selection is dome-shaped.

Backpack-mounted satellite transmitters do not affect reproductive performance in a migratory bustard

Backpack-mounted satellite transmitters (PTTs) are used extensively in the study of avian habitat use and of the movements and demography of medium- to large-bodied species, but can affect individuals’ performance and fitness. Transparent assessment of potential transmitter effects is important for both ethical accountability and confidence in, or adjustment to, life history parameter estimates. We assessed the influence of transmitters on seven reproductive parameters in Asian houbara Chlamydotis macqueenii, comparing 114 nests of 38 females carrying PTTs to 184 nests of untagged birds (non-PTT) over seven breeding seasons (2012–2018) in Uzbekistan. There was no evidence of any influence of PTTs on: lay date (non-PTT x̅ = 91.7 Julian day ± 12.3 SD; PTT x̅ = 95.1 Julian day ± 15.7 SD); clutch size (non-PTT x̅= 3.30 ± 0.68 SD; PTT x̅ = 3.25 ± 0.65 SD); mean egg weight at laying (non-PTT x̅ = 66.1 g ± 5.4 SD; PTT x̅ = 66.4 g ± 5.4 SD); nest success (non-PTT x̅ = 57.08% ± 4.3 SE; PTT x̅ = 58.24% ± 4.5 SE for nests started 2 April); egg hatchability (non-PTT x̅ = 88.3% ± 2.2 SE; PTT x̅ = 88.3% ± 2.6 SE); or chick survival to fledging from broods that had at least one surviving chick (non-PTT x̅ = 63.4% ± 4.2 SE; PTT x̅ = 64.4% ± 4.7 SE). High nesting propensity (97.3% year−1 ± 1.9% SE) of tagged birds indicated minimal PTT effect on breeding probability. These findings show that harness-mounted transmitters can give unbiased measures of demographic parameters of this species, and are relevant to other large-bodied, cursorial, ground-nesting birds of open habitats, particularly other bustards.

Intraspecific demography of the silky shark (Carcharhinus falciformis): implications for fisheries management

Abstract The silky shark (Carcharhinus falciformis) is one of the most heavily fished tropical shark species globally, and currently there is increasing concern for its conservation status. However, large differences and ambiguity in life history parameter estimates among regions complicates its conservation and fisheries management. Using a Leslie matrix model that incorporated stochastic effects, we analysed the intraspecific demography of C. falciformis using available life history data from seven regions. Among regions, large differences were observed in generation time and age-specific reproductive contributions. Carcharhinus falciformis generally had low resilience to fishing mortality (F) throughout its distribution. Age-at-first-capture and age-at-last-capture management approaches resulted in substantial differences among regions. This was largely influenced by age-at-maturity. However, in scrutinizing some regional life history studies, it is likely that sampling design and methodological differences among regions have resulted in inaccuracies in life history parameter estimates and subsequent demographic attributes. This implies that age and life-stage-dependent management approaches using these possibly inaccurate life history parameters may be inappropriate. We suggest that a greater emphasis needs to be placed on eliminating human sources of error in elasmobranch life history studies to ensure management for wide-ranging species, such as C. falciformis, is most effective.

A seasonal population matrix model of the Caribbean Red‐tailed Hawk Buteo jamaicensis jamaicensis in eastern Puerto Rico

Reliable estimates of life history parameters and their functional role in animal population trajectories are critical, yet often missing, components in conservation and management. We developed seasonal matrix population models of the Red‐tailed Hawk Buteo jamaicensis jamaicensis in the upper and lower forests of the Luquillo Mountains, Puerto Rico, to describe the influence of early life stages (nestling and clutch survival) on population growth. Modelled populations exhibited positive discrete rates of growth in forests above 400 m (λ highlands = 1.05) and in forests below 400 m (λ lowlands = 1.27) of the Luquillo Mountains. Further, adult survival was the parameter with the highest proportional effect and direct contribution to growth of the population. Besides survival of adults, our results identified that nestling survival had the second greatest influence on λ, stressing the importance of this life stage for the population growth rate of Red‐tailed Hawks in our study area. Seasonal matrices are not commonly used to describe population dynamics of birds. However, these may be a useful tool to analyse the influence of life stages in the annual cycle to better address conservation and management needs, especially for species inhabiting oceanic islands.

Reproduction and morphology of Central American and Tres Marias spinner dolphins in the eastern tropical Pacific

AbstractFour geographic forms of spinner dolphin (Stenella longirostris) occur in the eastern tropical Pacific. Two of the forms are pelagic: the eastern and whitebelly, and two are coastal: the Central American and Tres Marias spinner dolphins. Of these, only the Tres Marias form lacks recognition appropriate for developing management and conservation plans. Vertical aerial photographs of 57 spinner dolphin schools taken between 1988 and 2006 were used to examine the range of coastal forms and to characterize their calving seasons. On the basis of adult body length, spinner dolphins photographed off Guerrero, Mexico, were identified as those of the Central American form, which is north of their known range, and those photographed farther north, approximately 112 km off Nayarit, Mexico, were identified as the Tres Marias form. Calving peaked from October through March, and there was evidence that calving seasons differed among geographic forms with coastal forms calving later than pelagic forms. We present the first life history parameter estimates for the coastal forms of spinner dolphins, provide additional support for recognition of the Tres Marias form, and the first evidence of the Central American form occurring north of the Gulf of Tehuantepec, Mexico.

Yield-per-recruit modeling of two piscivores in a Midwestern reservoir: A Bayesian approach

Walleye Sander vitreus and hybrid striped bass Morone chrysops x M. saxatilis fisheries are supported by annual stockings in many US midwestern reservoirs. To maximize return to the angler, yield-per-recruit models are often used to evaluate expected yield and assist managers to determine which regulation to implement, generally length or bag limits. However, yield-per-recruit models are typically formulated with point estimates of life history parameters, which ignore uncertainty. Our objective was to estimate yield from yield-per-recruit models of walleye and hybrid striped bass under various harvest strategies (e.g., alternative minimum length limits and conditional fishing mortality rates) while incorporating uncertainty about the input model parameters. We estimated parameters of age and growth and weight-length models simultaneously using Bayesian inference. The full posterior distribution of these model parameter estimates were then used to estimate yield. We found that yield differed among length limits for both species at high conditional fishing mortality. We also found yield decreased for both species as minimum length limits increased for low conditional fishing mortality. Finally, we presented a probabilistic framework to determine how changing minimum length limits and conditional fishing mortality affects the probability of achieving 70–90% of the maximum yield. Our results provide insight on the expected yield under different minimum length limits and bag limits, while incorporating uncertainty in the model inputs, and add to the sparse literature on hybrid striped bass population dynamics.

Shark Interactions With Directed and Incidental Fisheries in the Northeast Pacific Ocean: Historic and Current Encounters, and Challenges for Shark Conservation.

For over 100 years, sharks have been encountered, as either directed catch or incidental catch, in commercial fisheries throughout the Northeast Pacific Ocean. A long-standing directed fishery for North Pacific Spiny Dogfish (Squalus suckleyi) has occurred and dominated shark landings and discards. Other fisheries, mainly for shark livers, have historically targeted species including Bluntnose Sixgill Shark (Hexanchus griseus) and Tope Shark (Galeorhinus galeus). While incidental catches of numerous species have occurred historically, only recently have these encounters been reliably enumerated in commercial and recreational fisheries. In this chapter we present shark catch statistics (directed and incidental) for commercial and recreational fisheries from Canadian waters (off British Columbia), southern US waters (off California, Oregon, and Washington), and northern US waters (off Alaska). In total, 17 species of sharks have collectively been encountered in these waters. Fishery encounters present conservation challenges for shark management, namely, the need for accurate catch statistics, stock delineation, life history parameter estimates, and improved assessments methods for population status and trends. Improvements in management and conservation of shark populations will only come with the further development of sound science-based fishery management practices for both targeted and incidental shark fisheries.

A stepwise stochastic simulation approach to estimate life history parameters for data-poor fisheries

Coastal fisheries are typically characterized by species-rich catch compositions and limited management resources, which typically leads to notably data-poor situations for stock assessment. Some parsimonious stock assessment approaches rely on cost-efficient size composition data, but these also require estimates of life history parameters associated with natural mortality, growth, and maturity. These parameters are unavailable for most exploited stocks. Here, we present a novel approach that uses a local estimate of maximum length and statistical relationships between key life history parameters to build multivariate probability distributions that can be used to parameterize stock assessment models in the absence of species-specific life history data. We tested this approach on three fish species for which empirical length-at-age and maturity data were available (from Hawaii and Guam) and calculated probability distributions of spawning potential ratios (SPR) at different exploitation rates. The life history parameter and SPR probability distributions generated from our data-limited analytical approach compared well with those obtained from bootstrap analyses of the empirical life history data. This work provides a useful new tool that can greatly assist fishery stock assessment scientists and managers in data-poor situations, typical of most of the world’s fisheries.

Age validation of the North Atlantic stock of wreckfish (Polyprion americanus), based on bomb radiocarbon (14C), and new estimates of life history parameters

Age validation of the North Atlantic stock of wreckfish (Polyprion americanus), based on bomb radiocarbon (14C), and new estimates of life history parameters

Age and growth parameters of shark‐like batoids

Estimates of life-history parameters were made for shark-like batoids of conservation concern Rhynchobatus spp. (Rhynchobatus australiae, Rhynchobatus laevis and Rhynchobatus palpebratus) and Glaucostegus typus using vertebral ageing. The sigmoid growth functions, Gompertz and logistic, best described the growth of Rhynchobatus spp. and G. typus, providing the best statistical fit and most biologically appropriate parameters. The two-parameter logistic was the preferred model for Rhynchobatus spp. with growth parameter estimates (both sexes combined) L(∞) = 2045 mm stretch total length, LST and k = 0·41 year⁻¹. The same model was also preferred for G. typus with growth parameter estimates (both sexes combined) L∞ = 2770 mm LST and k = 0·30 year⁻¹. Annual growth-band deposition could not be excluded in Rhynchobatus spp. using mark-recaptured individuals. Although morphologically similar G. typus and Rhynchobatus spp. have differing life histories, with G. typus longer lived, slower growing and attaining a larger maximum size.